1. Field of the Invention
The present invention relates to an assembly for measuring the surface level and the specific gravity of a liquid.
2. Background Art
Many systems, both industrial and non-industrial, utilize liquid. For example, water, or liquids consisting primarily of water, are often used as a coolant. Acids, used for example in lead-acid batteries, and liquid desiccants, used in dehumidification or water collection systems, are also frequently used. Depending on the system, a knowledge of the characteristics of the liquid at some given time may be important.
In particular, it may be important to know what volume of liquid is available in a system. In the case of liquid residing in a container having a regular shape and a fixed volume, one way to determine the volume of liquid present is to measure the liquid level. Another important characteristic of the liquid may be its specific gravity, which could be indicative of the concentration of constituent materials making up the liquid.
Some systems for measuring the level and specific gravity of a liquid are only able to measure an increase or decrease in the specific gravity or liquid level as they relate to one another. In conventional systems, when there is a change in either the liquid level or specific gravity, the system detects and then outputs a single signal indicating such a change. These systems are unable to determine whether the detected change is attributable to a change in the liquid level or the specific gravity, and therefore, are of limited utility. They provide only general information, which may not be adequate in many applications. Such systems are only able to indicate that one or both of the liquid level and specific gravity have changed, without indicating which has occurred.
One system that combines measurement of liquid level and specific gravity is U.S. Pat. No. 3,994,175 (“the '175 patent”), entitled “Device for Detecting Specific Gravity and Liquid Level of a Liquid,” issued on Nov. 30, 1976. The '175 patent describes a system where a voltage signal is created when the liquid level, the specific gravity, or a combination of the two, falls below a predetermined level. When this occurs, the signal triggers an alarm indicating that either one or both of these parameters has fallen below the critical level. Although the system described in the '175 patent is affected by both liquid level and specific gravity, it is unable to indicate a change in either of these values independently of the other.
Another limitation of conventional systems is that they may not operate in a corrosive environment. Measurement devices comprising metallic materials do not operate well, or at all, in corrosive environments, such as in desiccant in a water management system, or in acid in batteries. Finally, many conventional systems are expensive to manufacture. These systems generally require two separate devices to measure both the liquid level and the specific gravity of the liquid. This can be expensive, cumbersome and require an inefficient use of space. Therefore, it would be desirable to have a system that can independently measure and display readings of both the liquid level and the specific gravity of a liquid utilizing a single, integrated device. A need also exists for such a system that can operate well in a corrosive environment, and is cost effective to manufacture.